1. Technical Field of the Invention
The present invention relates to an ink jet head for an ink jet type recording apparatus and more particularly to a method of adjusting the characteristics of the piezoelectric material used for the ink jet head.
2. Description of Related Art
Most conventional ink jet heads are of a type in which ink drops are ejected by pressure resulting from the deformation of an electromechanical transducer such as piezoelectric materials so as to print dots on a recording medium. The electromechanical transducer is in the shape of a plate of a piezoelectric material and forms the walls of ink pressure chambers. The walls oppose each other, defining the ink pressure chamber therebetween. A voltage is applied to the piezoelectric material so as to drive the opposed plates to vibration, the vibration causing the ink in the ink pressure chamber to be ejected through an orifice. This operation is referred to as "drop-on-demand", since the ink is ejected when it is actually demanded.
Recent needs for high speed and high density printing, and color printing place demands on piezoelectricity type ink jet heads to provide a high packing density, a small sized unit, an increased number of ink channels, and an increased drive frequency of ink channels. In order to accommodate such needs, a larger number of piezoelectric elements for printing a single color must be fabricated with a high density. For high definition printing, ink drops must be more closely controlled for stable amounts of ink contained therein and more accurate dot locations when printed on the print medium. Such close control of the ink drops requires controlled speeds of the ejected ink drops. However, the ink-ejecting pressures of many densely fabricated ink chambers vary from chamber to chamber due to manufacture variation, resulting in variations in the amount of ink contained in an ink drop and variations in the speed of the ink drop. This leads to poor yield of ink jet heads during manufacture.